Bifurcated stent and method for the manufacture and delivery of same

ABSTRACT

An expandable bifurcated stent comprising a proximal end and a distal end in communication with one another. The proximal end comprises a primary passageway and the distal end comprises a pair of secondary passageways. The stent is expandable from a first, contracted position to a second, expanded position upon the application of a radially outward force exerted on the stent. Each of the primary passageway and the secondary passageway being constructed of has a porous surface. A method for production of a bifurcated stent is also described. Preferably, the method comprises the step of connecting a first stent section to a second stent section, the first stent section having an end thereof adapted for connection to an opening disposed along the length of a second stent section.

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/605,189, filed Feb. 28, 1996, now U.S. Pat. No. 5,755,771,issued May 26, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bifurcated stent and to a method forthe manufacture and delivery of a bifurcated stent.

2. Description of the Prior Art

Stents are generally known. Indeed, the term "stent" has been usedinterchangeably with terms such as "intraluminal vascular graft" and"expansible prosthesis". As used throughout this specification the term"stent" is intended to have a broad meaning and encompasses anyexpandable prosthetic device for implantation in a body passageway(e.g., a lumen or artery).

In the past six to eight years, the use of stents has attracted anincreasing amount of attention due the potential of these devices to beused, in certain cases, as an alternative to surgery. Generally, a stentis used to obtain and maintain the patency of the body passageway whilemaintaining the integrity of the passageway. As used in thisspecification, the term "body passageway" is intended to have a broadmeaning and encompasses any duct (e.g., natural or iatrogenic) withinthe human body and can include a member selected from the groupcomprising: blood vessels, respiratory ducts, gastrointestinal ducts andthe like.

Initial stents were self-expanding, spring-like devices which wereinserted in the body passageway in a contracted state. When released,the stent would automatically expand and increase to a final diameterdependent on the size of the stent and the elasticity of the bodypassageway. Such stents are known in the art as the Wallstent™.

The self-expanding stents were found by some investigators to bedeficient since, when deployed, they could place undue, permanent stresson the walls of the body passageway. This lead to the development ofvarious stents which were controllably expandable at the target bodypassageway so that only sufficient force to maintain the patency of thebody passageway was applied in expanding the stent.

Generally, in these later systems, a stent, in association with aballoon, is delivered to the target area of the body passageway by acatheter system. Once the stent has been properly located (the targetarea of the body passageway can be filled with a contrast medium tofacilitate visualization during fluoroscopy), the balloon is expandedthereby expanding the stent, e.g. by plastic deformation of the stentstructure, so that the latter is urged in place against the bodypassageway. As indicated above, the amount of force applied is at leastthat necessary to maintain the patency of the body passageway. At thispoint, the balloon is deflated and withdrawn within the catheter, andsubsequently removed. Ideally, the stent will remain in place andmaintain the target area of the body passageway substantially free ofblockage (or narrowing).

A stent which has gained some notoriety in the art is known as thePalmaz-Schatz™ Balloon Expandable Stent (hereinafter referred to as "thePalmaz-Schatz stent"). This stent is discussed in a number of patentsincluding U.S. Pat. Nos. 4,733,665, 4,739,762, 5,102,417 and 5,316,023,the contents of each of which are hereby incorporated by reference.

Another stent which has gained some notoriety in the art is known asGianturco-Roubin Flex-Stent™ (hereinafter referred to as "theGianturco-Roubin stent"). This stent is discussed in a number of patentsincluding U.S. Pat. Nos. 4,800,882, 4,907,336 and 5,041,126, thecontents of each of which are hereby incorporated by reference.

Other types of stents are disclosed in the following patents:

U.S. Pat. No. 5,035,706 (Gianturco et al.),

U.S. Pat. No. 5,037,392 (Hillstead),

U.S. Pat. No. 5,147,385 (Beck et al.),

U.S. Pat. No. 5,282,824 (Gianturco),

Canadian patent 1,239,755 (Wallsten), and

Canadian patent 1,245,527 (Gianturco et al.),

the contents of each of which are hereby incorporated by reference.

All of the stents described in the above-identified patents share thecommon design of being mono-tubular and thus, are best suited to bedelivered and implanted in-line in the body passageway. These knownstents are inappropriate for use in a bifurcated body passageway (e.g. abody passageway comprising a parent passageway that splits into a pairof passageways). Further, these stents are inappropriate for use in abody passageway having side branches since: (i) accurate placement ofthe stent substantially increases the risk to the patient, (ii) the riskof passageway closure in the side branches is increased, and (iii) theside branches will be substantially inaccessible.

Indeed the Physician Guide published in support of the Palmaz-Schatzstent states on page 32 (the contents of which are hereby incorporatedby reference):

". . . no attempt should be made following placement of a PALMAZ-SCHATZstent to access the side branch with a guide wire or a balloon, as suchattempts may result in additional damage to the target vessel or thestent. Attempts to treat obstructed side branches within stentedsegments can result in balloon entrapment, necessitating emergencybypass surgery."

Thus, when installed, the Palmaz-Schatz stent admittedly shields sidebranches emanating from the target area of the body passagewayeffectively permanently. This can be problematic since the only way totreat blockage or other problems associated with the side branches is toperform the type of surgery which installation of the stent was intendedto avoid.

This contraindication for conventional mono-tubular stents iscorroborated by a number of investigators. See, for example, thefollowing:

1. Interventional Cardiovascular Medicine: Principles and Practice(1994); Publisher: Churchill Livingstone Inc.; pages 221-223 (Ohman etal.), 487-488 (Labinaz et al.), 667-668 (Bashore et al.) and 897 (Baileyet al.), including references cited therein;

2. Gianturco-Roubin Flex-Stent™ Coronary Stent: Physician's Guide; page2, Paragraph 3 under WARNINGS;

3. Circulation, Vol. 83, No. 1, January 1991 (Schatz et al.); entitled"Clinical Experience With the Palmaz-Schatz Coronary Stent"; pages148-161 at page 149; and

4. American Heart Journal, Vol. 127, No. 2, February 1994 (Eeckhout etal.); entitled "Complications and follow-up after intracoronarystenting: Critical analysis of a 6-year single-center experience"; pages262-272 at page 263,

the contents of each of which are hereby incorporated by reference.

Further, some investigators have attempted to install individual stentsin each branch of the bifurcated body passageway. However, this approachis fraught with at least two significant problems. First, implantationof three individual stents, together with the expansive forces generatedupon implantation results in subjecting the central walls of thebifurcated body passageway to undue stress which may lead topost-procedural complications. Second, since the central walls of thebifurcated body passageway are not supported by the individual stents,this area of the passageway is left substantially unprotected andsusceptible to blockage.

One particular problem area with bifurcated body passageways is theoccurrence of bifurcation lesions within the coronary circulation.Generally, these legions may be classified as follows:

    ______________________________________    Type Characteristic    ______________________________________    A    Prebranch stenosis not involving the ostium of         the side branch;    B    Postbranch stenosis of the parent vessel not involving the         origin of the side branch;    C    Stenosis encompassing the side branch but not involving         the ostium;    D    Stenosis involving the parent vessel and ostium of         the side branch;    E    Stenosis involving the ostium of the side branch only;         and    F    Stenosis discretly involving the parent vessel and ostium         of the side branch.    ______________________________________

See Atlas of Interventional Cardiology (Popma et al.), 1994, pages77-79, the contents of which are hereby incorporated by reference. Thepresence of bifurcation lesions is predictive of increased proceduralcomplications including acute vessel closure.

Detailed classification of other bifurcated body passageways isrelatively undeveloped given the lack of non-surgical treatmentapproaches.

U.S. Pat. No. 4,994,071 (MacGregor) discloses a bifurcating stentapparatus. The particular design incorporates a series of generallyparallel oriented loops interconnected by a sequence of "half-birch"connections. The lattice structure of the illustrated stent isconstructed of wire. The use of such wire is important to obtain theloop structure of the illustrated design. The use of a wire loopconstruction is disadvantageous since it is complicated to manufactureand the resulting stent is subject to expansion variability (e.g.variable post-expansion distortion and the like).

U.S. Pat. Nos. 3,993,078 (Bergentz et al.) and 5,342,387 (Summers) alsodisclose and illustrate a bifurcated stent design constructed of wire.These designs suffer from the same disadvantages as the design describedin the previous paragraph.

It would be desirable to have a reliable, expandable bifurcated stentsince this would be useful in treating aneurysms, blockages and otherailments. It would be further desirable to have a practical method forproducing such a stent. It would also be desirable if such a stent wasrelatively easy to install.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel expandablebifurcated stent which obviates or mitigates at least one of theabove-mentioned disadvantages of the prior art.

It is another object of the present invention to provide a novel methodfor the manufacture of an expandable bifurcated stent.

It is another object of the present invention to provide a novel methodfor implanting an expandable bifurcated stent.

Accordingly, in one of its aspects, the present invention provides anexpandable bifurcated stent comprising a proximal end and a distal endin communication with one another, the proximal end comprising a primarypassageway and the distal end comprising a pair of secondarypassageways, each secondary passageway in communication with the primarypassageway at a first intersection, the stent being expandable from afirst, contracted position to a second, expanded position upon theapplication of a radially outward force exerted on the stent, each ofthe primary passageway and the secondary passageways, being constructedof a tubular wall having a porous surface, at least one connectionportion being disposed at the first intersection for reinforcing thefirst intersection.

In another of its aspects, the present invention provides expandablebifurcated stent comprising a proximal end and a distal end incommunication with one another, the proximal end comprising a primarypassageway and the distal end comprising a pair of secondarypassageways, each secondary passageway in communication with the primarypassageway at a first intersection, the stent being expandable from afirst, contracted position to a second, expanded position upon theapplication of a radially outward force exerted on the stent, each ofthe primary passageway and the secondary passageways having a poroussurface, at least one connection portion interconnecting the pair ofsecondary passageways for reinforcing the first intersection.

In yet another of its aspects, the present invention provides a methodfor production of a bifurcated stent comprising the step of connecting afirst stent section to a second stent section, the first stent sectionhaving an end thereof adapted for connection to an opening disposedalong the length of a second stent section.

In yet another of its aspects, the present invention provides a methodfor production of a bifurcated stent comprising the steps of:

(i) connecting a first stent section to a second stent section toprovide a connection portion;

(ii) provide an opening in the connection portion;

(iii) connecting a third stent section to the connection portion.

In yet another of its aspects, the present invention provides a methodfor production of a bifurcated stent comprising the steps of:

passing a first stent section having a first opening disposed along alength thereof through a second stent section having a second openingdisposed along a length thereof, the first stent section having adiameter less than a diameter of the second stent section;

passing a leading end of the first stent section through the secondopening of the second stent section; and

substantially aligning the first opening and the second opening withrespect to one another.

In yet another of its aspects, the present invention provides a methodfor delivery to a target body passageway of an expandable bifurcatedstent comprising a proximal end and a distal end in communication withone another, the proximal end comprising a primary passageway and thedistal end comprising a pair of secondary passageways, the stent beingexpandable from a first, contracted position to a second, expandedposition upon the application of a radially outward force exerted on thestent, each of the primary passageway and the secondary passageway beingconstructed of a tubular wall having a porous surface, the methodcomprising the steps of:

disposing the stent in the first, contracted position on a catheter;

inserting the stent and catheter within the target body passageway bycatheterization of the target body passageway;

exerting a radially outward expansive force on the stent such that thestent assumes the second, expanded position and is urged against thetarget body passageway.

Thus, an aspect of the present invention relates to the provision of anexpandable bifurcated stent constructed of a tubular wall having aporous surface. As used throughout this specification, the term "tubularwall", when used in relation to a stent, is intended to mean asubstantially cylindrical tube which subsequently has been subjected toan etching (e.g. by laser, chemical or other suitable means) or similartechnique to remove pre-selected portions of the cylindrical tubethereby providing a porous surface on the tube--this is distinct from astent constructed of wire bent to a selected shape/design. To theknowledge of the Applicant's, an expandable bifurcated stent having sucha tubular wall has heretofore been unknown.

As used throughout this specification, the term "bifurcated stent" isintended to have a broad meaning and encompasses any stent having aprimary passageway to which is connected at least two secondarypassageways. Thus, trifurcated stents are encompassed herein. Further,one of the secondary passageways can be a continuation of the primarypassageway with the result that the other secondary passageway isessentially a side branch to the primary passageway.

The Applicant's have also discovered that various repeating patterns inthe porous surface of the tubular wall are particularly advantageous.Generally, the repeating pattern is a polygon having a pair of sidewalls substantially parallel to the longitudinal axis of the stentpassageway in question, a first concave-shaped wall and a secondconvex-shaped wall connecting the side walls. The various repeatingpatterns which are useful in the context of the present invention aredisclosed in the following copending patent applications filed in thename of the assignee of the present invention:

Canadian patent application number 2,134,997 (filed Nov. 3, 1994);

Canadian patent application number 2,171,047 (filed Mar. 5, 1996);

Canadian patent application number 2,175,722 (filed May 3, 1996);

Canadian patent application number 2,185,740 (filed Sep. 17, 1996);

International patent application PCT/CA97/00151 (filed Mar. 5, 1997);and

International patent application PCT/CA97/00152 (filed Mar. 5, 1997);

the contents of each of which are hereby incorporated by reference(hereinafter collectively referred to as the "Divysio patentapplications").

The present bifurcated stent may be constructed from any suitablestarting material. Preferably, the starting material is a thin tube of ametal or alloy (non-limiting examples include stainless steel, titanium,tantalum, nitinol, Elgiloy, NP35N and mixtures thereof) which would thenhave sections thereof cut or etched out to leave a repeating pattern,inter alia, such as one or more of those disclosed in the Divysio patentapplications.

The stent of the present invention may further comprise a coatingmaterial thereon. The coating material may be disposed continuously ordiscontinuously on the surface of the stent. Further, the coating may bedisposed on the interior and/or the exterior surface(s) of the stent.The coating material may be one or more of a biologically inert material(e.g. to reduce the thrombogenicity of the stent), a medicinalcomposition which leaches into the wall of the body passageway afterimplantation (e.g. to provide anticoagulant action, to deliver apharmaceutical to the body passageway and the like) and the like.

The stent is preferably provided with a biocompatible coating, in orderto minimize adverse interaction with the walls of the body vessel and/orwith the liquid, usually blood, flowing through the vessel. The coatingis preferably a polymeric material, which is generally provided byapplying to the stent a solution or dispersion of preformed polymer in asolvent and removing the solvent. Non-polymeric coating material mayalternatively be used. Suitable coating materials, for instancepolymers, may be polytetraflouroethylene or silicone rubbers, orpolyurethanes which are known to be biocompatible. Preferably, however,the polymer has zwitterionic pendant groups, generally ammoniumphosphate ester groups, for instance phosphoryl choline groups oranalogues thereof. Examples of suitable polymers are described inpublished International patent applications WO-A-93/16479 andWO-A-93/15775. Polymers described in those specifications arehemo-compatible as well as generally biocompatible and, in addition, arelubricious. When a biocompatible coating is used, it is important toensure that the surfaces of the stent are completely coated in order tominimize unfavourable interactions, for instance with blood, which mightlead to thrombosis.

This good coating can be achieved by suitable selection of coatingconditions, such as coating solution viscosity, coating technique and/orsolvent removal step.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described with reference tothe accompanying drawings wherein like numerals designate like parts andin which:

FIG. 1 illustrates a side elevation of a bifurcated stent in accordancewith the present invention;

FIGS. 2-4 illustrate a first embodiment of a method for production of abifurcated stent;

FIG. 5 illustrates a second embodiment of a method for production of abifurcated stent;

FIGS. 6a and 6b illustrate a post-treatment of a bifurcated stent whichhas been produced according to the methods illustrated in FIGS. 2-5;

FIGS. 7 and 8 illustrate a third embodiment of a method for productionof a bifurcated stent;

FIG. 9 illustrates a post-treated bifurcated stent which has beenproduced according to the method illustrated in FIGS. 7 and 8;

FIGS. 10 and 11 illustrate a fourth embodiment of a method forproduction of a bifurcated stent;

FIG. 12 illustrates a cross-section of a bifurcated body passageway intowhich the a bifurcated stent produced according to the present method ofmanufacture is being delivered;

FIG. 13 illustrates a cross-section of a bifurcated body passageway inwhich the bifurcated stent is positioned in a first, contractedposition;

FIG. 14 illustrates a cross-section of a bifurcated body passageway inwhich the bifurcated stent is positioned in a second, expanded position;

FIGS. 15 and 16 illustrate a side elevation of another bifurcated stentin accordance with the present invention;

FIGS. 17-22 illustrate various preferred features of the bifurcatedstent illustrated in FIGS. 15 and 16.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, there is illustrated a stent 10. Stent 10comprises a proximal end 15 and a distal end 20. Proximal end 15comprises a primary passageway 25. Distal end 20 comprises a pair ofsecondary passageways 30,35. Secondary passageways 30,35 are connectedto primary passageway 25 at an intersection point 40.

As will be apparent to those of skill in the art, stent 10 incorporatesthe porous surface design illustrated in copending Canadian patentapplication number 2,134,944, referred to above. As discussed above,this design may be varied to incorporate other designs such as thosedisclosed in the other Divysio patent applications.

With reference to FIGS. 2-4, an embodiment of the present method forproduction of a bifurcated stent is illustrated. For ease ofillustration, the porous surface of the tubular wall of the stent is notillustrated.

As illustrated, a first stent section 45 comprises a cylindrical tubehaving a bevelled cut 50 made adjacent one end of the cylindrical tube.Those of skill in the art will recognize that bevelled cut 50 may beincorporated into first stent section 45 during or after the productionof first stent section 45. Specifically, it is possible to produce firststent section 45 having a pre-selected porous design which includesbevelled cut 50 via a computer programmable, high precision laseretching technique. Alternatively, it is possible to use another etchingtechnique to produce first stent section 45 without bevelled cut 50 andthereafter use a precision jig or other means to cut first stent section45 to produce bevelled cut 50.

Similarly, a second stent section 55 is provided and includes radialcuts 56,57 and a longitudinal cut 58. Radial cuts 56,57 and longitudinalcuts 58 may be produced in second stent section 55 in the mannerdiscussed in the previous paragraph with respect to the production ofbevelled cut 50 in first stent section 45. Thereafter, a flap portion 51of first stent section 45 is folded away from bevelled cut 50.Similarly, a pair of flap 52,53 are folded away from longitudinal cut 58to expose an opening 54.

First stent section 45 is then lowered to cover opening 54 of secondstent section 55. Flaps 52,53 are folded to overlap a portion of firststent section 45. Flap 51 is folded to overlap a portion of second stentsection 55. With reference to FIG. 4, it is particularly preferred toadapt the geometry of flaps 52,53 of second stent section 55 such thatvarious of the struts disposed in flaps 52,53 overlap with or arejuxtaposed (in plan view) along at least a portion of the length thereofwith the struts on first stent section 45 (this is illustrated in moredetail hereinbelow with reference to FIG. 16). Preferably, the degree ofsuch overlap or juxtaposition is sufficient to:

(i) facilitate affixing the flaps 52,53 of second stent section 55 tofirst stent section 45;

(ii) achieve uniform expansion of the stent junction without occurrenceof substantial distortion; and

(iii) avoid the occurrence of "stent trap" or "stent jail" (usually theresult of cracking, buckling or other distortion at the junction of adeployed bifurcated stent making difficult or impossible to deliver afurther stent through the stent).

At this point, the flaps may be secured to the respective stent sectionsby any suitable means such as spot welding (e.g. by a laser or othersuitable means), loops, clips and the like. The preferred method ofaffixing the flaps to the respective stent section is to spot weld them.

A particular advantage of the process illustrated in FIGS. 2-4 is thatintersection point 40 (FIG. 1--overlapping flaps not illustrated forclarity) of the resulting stent is reinforced by virtue of dispositionof the flaps overlapping a portion of the respective stent sections.

As will be apparent to those of skill in the art, in certaincircumstances, it may be possible and even desirable to reduce the sizeof or even eliminate flap 51. Further, in certain circumstances, it maybe possible or ever desirable to trim one or both of flaps 52,53 priorto connection of first stent section 45 to second stent section 55.

With reference to FIG. 5, there is illustrated another embodiment of thepresent method for manufacture of a bifurcated stent. In thisembodiment, flap 51 (FIGS. 2 and 3) is simply cut away from first stentsection 45a. Further, an oval opening 54a is cut into second stentsection 55a (i.e. there are no flaps affixed to second stent section55a). Stent section 45a is then lowered on and connected to second stentsection 55a. First stent section 45a and second stent section 55a may beconnected to another in the manner described hereinabove with referenceto FIG. 2-4.

With reference to FIG. 6a, there is illustrated the stent produced bythe methods illustrated in FIGS. 2-5. During production of the stent, itis desirable to minimize the angle between first stent section 45 andsecond stent section 55. Even with this effort, it is preferred that theadjacent termini of first stent section 45 and section stent section 55are subjected to application of gentle squeezing or other sufficientforce in the direction of arrows A to facilitate catheterization of thestent. The result of such post-production treatment of the stent isillustrated in FIG. 6b.

With reference to FIGS. 7 and 8, there is illustrated yet anotherembodiment of the present method for manufacture of a bifurcated stent.In this embodiment, a pair of first stent sections 45b are secured oraffixed to one another. Thereafter, an apex portion 46b of the resultingconstruction is removed exposing an opening 54b. A second stent section55b is then connected to opening 54b provided by the combination offirst stent sections 45b. The manner of securing second stent section55b to the periphery of opening 54b created by first stent sections 45bis not particularly restricted and may be effected as discussedhereinabove. As will be appreciated by those of skill in the art, it ispossible and, in certain circumstances, desirable, to have one or moreflaps on one or move of first stent sections 45b and second stentsection 55b. Such flaps would be used in the manner discussedhereinabove in respect of FIGS. 2-4 to overlap a portion of the oppositestent section.

With reference to FIG. 9, there is illustrated the stent producedaccording to the method illustrated in FIGS. 7 and 8 afterpost-treatment in the manner discussed above in respect of FIGS. 6a and6b. That is, first stent sections 45b are subjected to application ofgentle squeezing or other sufficient force in the direction of arrows Bto facilitate catheterization of the stent.

With reference to FIGS. 10 and 11, there is illustrated yet anotherembodiment of the present method for manufacture of a bifurcated stent.In this embodiment, a first stent section 45c is provided with anopening 54c. A second stent section 55c is provided with an opening 56c.Second stent section 55c has a diameter slightly less than that of firststent section 45c. The difference in diameter between first stentsection 45c and second stent section 55c is sufficient to enable coaxialmovement of the stent sections with respect to one another with causingdamage to either stent section.

As illustrated by arrow C in FIG. 10, the end of second stent section55c is coaxially fed into an end of first stent section 45c. Once theleading end of second stent section 55c reaches opening 54c of firststent section 45c, it is pulled through opening 54c as illustrated byarrow D in FIG. 10. Second stent section 55c is pulled through opening54c until opening 56c is aligned with opening 54c--this is illustratedby dashed oval E in FIG. 11.

When practising the method illustrated in FIGS. 10 and 11, care shouldbe taken to design openings 54c and 56c so that they are in alignmentwhen the trailing end of second stent section 55c is flush with thetrailing end of first stent section 45c. Further, region F (FIG. 11) ofthe resulting bifurcated stent is "double reinforced" since it containsa coaxial disposition of first stent section 45c and second stentsection 55c. Accordingly, it is possible and, in some cases evendesirable, to modify the design of the respective stent sections in thisregion so that the overall expansion and relative flexibility/rigidityof the stent in this region is commensurate with that of the remainingportion of the stent (i.e. the secondary passageways which branch offfrom region F in FIG. 11).

While the embodiment illustrated in FIGS. 10 and 11 illustrates theresultant bifurcated stent having a coaxial, overlapping arrangement ofstent sections flush at one end, it will be appreciated by those ofskill in the art that the length of first stent section 45c or secondstent section 55c may be shortened thereby minimizing the size of regionF in FIG. 11.

With reference to FIGS. 12-14, there is illustrated a bifurcated bodypassageway 150 comprised of a proximal passageway 155 and a pair ofdistal passageways 160,165. As illustrated, bifurcated body passageway150 comprises a Type "D" Bifurcation lesion having characteristicblockages 170,175,180.

Stent 10 is delivered to bifurcated body passageway 150 in the followingmanner. Initially, a pair of guidewires 185,190 are inserted intoproximal passageway 155 such that guidewire 185 enters distal passageway160 and guidewire 190 enters distal passageway 165. The manner by whichthe guidewires are inserted is conventional and within the purview of aperson skilled in the art.

As illustrated, stent 10 is positioned in association with a pair ofcatheters 195,200 (for clarity, the interior of stent 10 is not shown).Catheter 195 has associated with it a balloon 205. Catheter 200 hasassociated with it a balloon 210. Balloons 205,210 substantially fillprimary passageway 25 of stent 10. Balloon 205 substantially fillssecondary passageway 30 of stent 10. Balloon 210 substantially fillssecondary passageway 35 of stent 10.

The stent/catheter/balloon combination is delivered through proximalpassageway 155 with the aid of guidewires 185,190. As thestent/catheter/balloon combination approaches distal passageways160,165, predisposition of guidewires 185,190 serves to separatesecondary passageways 30,35 to be disposed in distal passageways160,165, respectively. Thus, as illustrated in FIG. 13, stent 10 ispositioned in place.

Once stent 10 is in position, balloons 205,210 are expanded resulting inimplantation of stent 10 in the corresponding interior surfaces ofproximal passageway 155 and distal passageways 160,165. Uponimplantation of stent 10, balloons 205,210 are collapsed. Thereafter,catheters 195,200 and guidewires 185,190 have been removed leaving theimplanted stent 10 shown in FIG. 14. As illustrated in FIG. 14,blockages 170,175,180 are bulged radially outwardly in combination withthe appropriate portions of proximal passageway 155 and distalpassageways 160,165 resulting in a reduction in the overall blockage inbifurcated body passage 150.

It will be apparent to those of skill in the art that implantation ofstent 10 can be accomplished by various other means. For example, it iscontemplated that it is possible to substitute the pair ofcatheter/balloon combinations illustrated in FIGS. 12 and 13 with asingle, bifurcated catheter/balloon design which mimics the design ofthe stent. Thus, in this modification, the balloon and guidewire wouldbe design to mimic the bifurcated design of the stent. As furtheralternative, it is contemplated that the stent can be made of a suitablematerial which will expand when bifurcated body passageway 150 isflushed with a liquid having an elevated temperature (e.g. 150° F.-160°F.). Further, stent 10 can be designed to expand upon the application ofmechanical forces other than those applied by a balloon/catheter. Stillfurther, stent 10 can be designed self-expanding (e.g. by constructingstent from material such as nitinol and the like) to be implanted asdescribed above. In this embodiment, the radially outward force exertedon the stent would be generated within the stent itself.

With reference to FIGS. 15-22, there is illustrated another preferredbifurcated stent in accordance with the present invention. As will beapparent to those of skill in the art, the stent illustrated in FIGS.15-22 shares many of the features of stent 10 illustrated in FIG. 1.

Thus, with reference to FIGS. 15 and 16, there is illustrated a stent100. FIG. 15 is a side elevation of stent 100 without the porous surfaceillustrated (for clarity). FIG. 16 is a side elevation of an enlargedportion of stent 100 with the porous surface illustrated. Stent 100comprises a proximal end 102 and a distal end 104. Proximal end 102comprises a primary passageway 103. Distal end 104 comprises a pair ofsecondary passageways 105,106. Secondary passageways 105,106 areconnected to primary passageway 103 at an intersection point 107--thenature of intersection point 107 will be further discussed hereinbelow.It is intersection point 107 which distinguishes stent 100 in FIG. 16from stent 10 in FIG. 1.

As will be apparent to those of skill in the art, stent 100 incorporatesthe porous surface design illustrated in copending Canadian patentapplication number 2,134,944, referred to above. As discussed above,this design may be varied to incorporate other designs such as thosedisclosed in the other Divysio patent applications.

With reference to FIGS. 17-19, manufacture of stent 100 will bediscussed. Generally, the manufacture of stent 100 is similar to themanufacture of stent 10 illustrated in FIGS. 1-4 and discussedhereinabove. The principle difference in the manufacture of stent 100 isthe use of a modified first stent section 108.

First stent section 108 is constructed from a substantially cylindricaltube 109. A porous surface 110 is disposed on a major portion ofcylindrical tube 109. A first connection tab 111 and a second connectiontab 112 are also disposed on cylindrical tube 109. As discussedhereinabove, it is possible to produce first section 108 comprisingporous 110, first connection tab 111 and second connection tab 112 usingcomputer programmable, high precision laser etching techniques or byother etching techniques in combination with precision jig techniques.This results in an end of porous surface 110 comprising first connectiontab 111, second connection tab 112 and a bevelled edge 113. The productof the cutting techniques is illustrated in FIG. 18.

FIG. 19 is an enlarged perspective view of a portion of first connectiontab 111 (second connection tab 112 is preferably the same). Asillustrated, first connection tab 111 comprises a stem 114 and a head115. Preferably, stem 114 and/or head 115 are curved to have a shapecomplementary to the outer surface of the second section to which firststent section 108 is connected (discussed in more detailed hereinbelow).Stem 114 and head 115 comprise a plurality of slots 116 disposedtherein. Slots 116 may be disposed in stem 114 and head 115 by the useof a computer programmable, high precision laser as described above.Preferably, slots 116 are disposed throughout the thickness of stem 114and head 115. Slots 116 may be may have a straight or taperedcross-section. Preferably, slots 116 have a thickness in the range offrom about 0.0015 to about 0.004 inches. Head 115 further comprisessolid (i.e., slot-free or non-porous) regions 117.

Thus, in the embodiment illustrated in FIG. 19, slots 116 serve to froma porous surface in first connection tab 111 (second connection tab 112is preferably the same). While it is preferred to have such a poroussurface disposed in the connection tabs, the precise nature of theporosity is not particularly restricted. The provision of a poroussurface, particularly at head 115, facilitates expansion of theconnection tab while minimizing or avoiding the occurrence of crackingor distortion.

After the production of first stent section 108, first connection tab111 and second connection tab 112 are bent or otherwise moved to besubstantially collinear with the periphery of bevelled edge 113 (i.e.,as illustrated in FIG. 118). At this point, first stent section 108 maybe connected to another stent section of a design similar to secondstent section 55 discussed hereinabove with reference to FIGS. 2-4--seeintersection point 107 in FIG. 16. In this embodiment, as in theembodiments illustrated in FIGS. 2-4, it is preferred to adapt thegeometry of flaps 52,53 of second stent section 55 such that various ofthe struts disposed in flaps 52,53 overlap along at a portion of thelength thereof with the struts on first stent section 108. See, forexample, regions G and H in FIG. 16 which illustrates an embodiment ofsuch partial overlap and juxtaposition (in plan view). Of Firstconnection tab 111 and second connection tab 112 may be secured to thesecond stent section as described above. Specifically, it isparticularly preferred to connect solid (i.e., non-porous) regions tothe section stent portion.

The benefits accruing from the use of first stent section 108 in theproduction a bifurcated stent include:

1. The provision of at least one solid (i.e., non-porous) region in theconnection tabs facilitates attachment of the respect stent sections toone another (e.g. laser welding is facilitated significantly);

2. The provision of a porous surface in at least a portion of theconnection tabs facilitates bending thereof for connection of therespective stent sections; and

3. The provision of slots 116, particularly in second connection tab 112(see FIG. 15), allows the slots to function as a solid state valve atthe "crotch" of the bifurcated stent thereby providing sealed,reinforcement of the bifurcated stent in this crucial region--this isillustrated in FIG. 20 which depicts tapered openings for slots 116 andthe apex of the bend in stem 114.

FIG. 21 illustrates an alternate embodiment of the embodimentillustrated in FIGS. 15-20. Specifically, in FIG. 21, second stentsection 55, otherwise the same as that described hereinabove withreference to FIGS. 1-4, is adapted to include a landing 119 forreceiving a solid (i.e. non-slot or non-porous) connection tab 120.Landing 119 may be connected to connection tab 120 as describedhereinabove.

With reference to FIG. 22, there is illustrated a variant to theembodiment illustrated in FIG. 21. Specifically, in FIG. 22, aconnection tab 121 having the entire surface thereof slotted andotherwise porous is connected to landing 119.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications of the illustrative embodiments,as well as other embodiments of the invention, will be apparent topersons skilled in the art upon reference to this description. Forexample, while first connection tab 111 and second connection tab 112have been illustrated as being attached to first stent portion 108, itis possible to have these tabs integral with second stent portion 55.Alternatively, the connection tabs do not have to integral with eitherof the stent portions and, instead, can be custom-designed, independentconnection tabs which are affixed to both stent portions. Still further,it is possible for the connection tabs (integral or independent) to havea different thickness than either of the stent sections. It is thereforecontemplated that the appended claims will cover any such modificationsor embodiments.

What is claimed is:
 1. An ex vivo expandable bifurcated stent comprisinga proximal end and a distal end in communication with one another, theproximal end comprising a primary passageway and the distal endcomprising a pair of secondary passageways, each secondary passagewaycoupled to the primary passageway at a first intersection, the stentbeing expandable from a first, contracted position to a second, expandedposition upon the application of a radially outward force exerted on thestent, each of the primary passageway and the second passageways beingconstructed of a tubular wall having a porous surface, at least onereinforcing member being disposed at the first intersection forreinforcing the first intersection, said reinforcing member overlappingat least one of (i) said primary passageway, (ii) a first of saidsecondary passageways, and (iii) a second of said secondary passageways,said reinforcing member being separate structure from same firstintersection.
 2. The bifurcated stent defined in claim 1, wherein thestent comprises a first stent section connected to a second stentsection.
 3. The bifurcated stent defined in claim 2, wherein an end ofthe first stent section is connected to an opening disposed along alength of the second stent section.
 4. The bifurcated stent defined inclaim 3, wherein a first connection portion is disposed at an end of thefirst stent section and is connected to the second stent section.
 5. Thebifurcated stent defined in claim 4, wherein the first connectionportion is integral with an end of the first stent section.
 6. Thebifurcated stent defined in claim 4, wherein the first connectionportion comprises a porous section and a non-porous section, thenon-porous section connected to the second stent section.
 7. Thebifurcated stent defined in claim 6, wherein the porous sectioncomprises a plurality of elongate slots.
 8. The bifurcated stent definedin claim 7, wherein the elongate slots traverse the thickness of atleast one connection tab.
 9. The bifurcated stent defined in claim 7,wherein the elongate slots are disposed substantially orthogonal to alongitudinal axis of the first stent section.
 10. The bifurcated stentdefined in claim 2, wherein the second stent section comprises a secondconnection portion along at least a portion of the periphery of theopening, the second connection portion connected to the first stentsection.
 11. The bifurcated stent defined in claim 2, wherein the firststent section and the second stent section are coaxially disposed withrespect to one another along at least a portion of the primarypassageway.
 12. The bifurcated stent defined in claim 2, wherein thefirst stent section and the second stent section are coaxially disposedwith respect to one another along substantially the entire length of theprimary passageway.
 13. The bifurcated stent defined in claim 2, whereinthe first stent section and the second stent section are connected toone another and to a third stent section, at least one of the stentsections comprising the primary passageway and each of the other tostent sections comprising a secondary passageway.
 14. The bifurcatedstent defined in claim 1, wherein the at least one connection portioninterconnects the pair of secondary passageways.
 15. The bifurcatedstent defined in claim 1, wherein the at least one connection portionconnects one of the pair of second passageways to the primarypassageway.
 16. A stent according to claim 1, wherein the reinforcingmember is integral with the first of said secondary passageways and iscoupled to the second of said secondary passageways.
 17. A stentaccording to claim 1, wherein the reinforcing member is integral withthe first of said secondary passageways and overlaps said primarypassageway.
 18. A stent according to claim 1, wherein said firstsecondary passageway and said second secondary passageway form a crotch,and wherein said reinforcing member is disposed in said crotch.
 19. Astent according to claim 1, wherein said reinforcing member extendscircumferentially less than the entire circumference of the passagewaywhich it overlaps.
 20. A stent according to claim 1, wherein anopen-faced end of one of said secondary passageways is coupled to acorresponding opening in said primary passageway.
 21. A stent accordingto claim 1, wherein said reinforcing member comprises a T-shaped tabwherein the top portion of said tab extends circumferentially around aportion of the overlapped passageway.
 22. A stent according to claim 1,wherein said reinforcing member extends from the second of saidsecondary passageways and overlaps said primary passageway, and furthercomprising a further reinforcing member which extends from said secondsecondary passageway and overlaps said first secondary passageway.
 23. Amethod for production of an ex vivo bifurcated stent comprising thesteps of:connecting a first stent section to a second stent section atan intersection, the first stent section having an end thereof adaptedfor connection to an opening disposed along the length of a second stentsection, each of said first stent section and said second stent sectionbeing constructed of a tubular wall having a porous surface; anddisposing a reinforcing member at an intersection between said firststent section and said second stent section, said reinforcing memberoverlapping at least one of (i) said first stent section, and (ii) saidsecond stent section, said reinforcing member being separate structurefrom the intersection between said first stent section and said secondstent section.
 24. The method defined in claim 23, wherein the end ofthe first stent section adapted for connection is bevelled with respectto a longitudinal axis of the first stent section.
 25. The methoddefined in claim 23, comprising the further step of disposing at leastone second flap portion at a periphery of the opening disposed along thelength of the second stent section.
 26. The method defined in claim 23,comprising the further step of disposing a pair of second flap portionsat a periphery of the opening disposed along the length of the secondstent section.
 27. The method defined in claim 26, wherein, prior to theconnecting step, at least one second flap portion is trimmed to areduced size.
 28. The method defined in claim 26, comprising the furtherstep of overlapping the at least one second flap portion of the secondstent section on to a portion of the first stent section.
 29. The methoddefined in claim 28, wherein the connecting step comprises welding theat least one second flap portion of the second stent section to thefirst stent section.
 30. The method defined in claim 26, wherein, priorto the connecting step, at least one second flap portion is removed. 31.The method defined in claim 23, comprising the further steps ofproducing the second stent section by:providing a pair of third stentsections, each third stent sections having an end thereof bevelled withrespect to a longitudinal axis of the third stent section; joining thepair of third stent sections in a complementary manner at each bevelledend thereof to provide a substantially V-shaped stent section; andremoving an apex portion of the V-shaped stent section to define thesecond stent section having an opening therein.
 32. The method definedin claim 31, wherein the connecting step comprises connecting the end ofthe first stent section to the opening defined in the V-shaped stentsection.
 33. The method defined in claim 23, wherein the connecting stepcomprises welding the first stent section to the second stent section.34. A method for production of a bifurcated stent comprising the stepsof:connecting a first stent section to a second stent section, the firststent section having an end thereof adapted for connection to an openingdisposed along the length of a second stent section; and disposing atleast one first flap portion at the end of the first stent sectionadapted for connection to a portion of the second stent section.
 35. Themethod defined in claim 34, wherein the at least one flap portioncomprises a connection tab having a non-porous surface disposed on atleast a portion thereof.
 36. The method defined in claim 34, wherein theat least one flap portion comprises a connection tab having a poroussurface disposed on at least a portion thereof.
 37. The method definedin claim 36, wherein the porous surface comprises a plurality ofsubstantially elongate slots.
 38. The method defined in claim 34,wherein the at least one flap portion comprises a connection tab havingboth a porous surface and non-porous surface disposed thereon.
 39. Themethod defined in claim 38, wherein the porous surface comprises aplurality of substantially elongate slots.
 40. The method defined inclaim 34, wherein the at least one first flap portion is produced byfolding from the end of the first stent section adjacent the bevelledcut.
 41. The method defined in claim 34, wherein, prior to theconnecting step, the at least one first flap portion is trimmed to areduced size.
 42. The method defined in claim 34, comprising the furtherstep of overlapping the at least one first flap portion of the firststent section on to a portion of the second stent section.
 43. Themethod defined in claim 42, wherein the connecting step compriseswelding the at least one first flap portion of the first stent sectionto the second stent section.
 44. The method defined in claim 34,wherein, prior to the connecting step, the at least one first flapportion is removed.
 45. A method for production of a bifurcated ex vivostent comprising the steps of:passing a first stent section having afirst opening disposed along a length thereof through a second stentsection having a second opening disposed along a length thereof, thefirst stent section having a diameter less than a diameter of the secondstent section, the first stent section and the second stent section eachcomprising a tubular wall having a porous surface; passing a leading endof the first stent section through the second opening of the secondstent section; substantially aligning the first opening and the secondopening with respect to one another at an intersection; and affixing thefirst stent section to the second stent section with a reinforcingmember that overlaps at least one of the first stent section and thesecond stent section, the reinforcing member being a separate structurefrom the intersection between the first stent section and the secondstent section.
 46. An expandable ex vivo bifurcated stent comprising aproximal end and a distal end in communication with one another, theproximal end comprising a primary passageway and the distal endcomprising a pair of secondary passageways, each secondary passageway incommunication with the primary passageway at a first intersection, thestent being expandable from a first, contracted position to a second,expanded position upon the application of a radially outward forceexerted on the stent, each of the primary passageway and the secondarypassageways having a porous surface, each of said primary passageway andsaid secondary passageway comprising a tubular wall, at least onereinforcing portion interconnecting the pair of secondary passagewaysfor reinforcing the first intersection, said reinforcing portionoverlapping at least one of the secondary passageways, said reinforcingportion being separate structure from the first intersection between theprimary passageway and the secondary passageways.